- Exclusion criteria will include a history of illicit drug or alcohol dependence, impaired hepatic (aspartate aminotransferase or alanine aminotransferase > 2x upper limit of normal range) or renal function (receiving dialysis or serum creatinine > 1.5 mg/dL), high-grade (> 1st degree) heart block, or known allergy to dexmedetomidine.